
"""
lwf的笔记, 和runtime里的稍有区别
Record of phased-in incompatible language changes.

Each line is of the form:

FeatureName = "_Feature(" OptionalRelease ",
                        " MandatoryRelease ",
                        "CompilerFlag ",
                        )"

        Normally,
        OptionalRelease < MandatoryRelease,
        and both are 5-tuples of the same form as sys.version_info:


            (PY_MAJOR_VERSION, # the 2 in 2.1.0a3; an int
            PY_MINOR_VERSION, # the 1; an int
            PY_MICRO_VERSION, # the 0; an int
            PY_RELEASE_LEVEL, # "alpha", "beta", "candidate" or "final"; string
            PY_RELEASE_SERIAL # the 3; an int
            )

    OptionalRelease records the first release in which

            from __future__ import FeatureName

        was accepted.

    MandatoryReleases
        if  MandatoryReleases that have not yet occurred:
            MandatoryRelease predicts the release in which
                the feature will become part of the language.


        elif MandatoryRelease 是 None,
            a planned feature got dropped.

        else
            MandatoryRelease records
            when the feature became part of the language;
                in releases at or  after that,
                modules no longer need

                    ¿from __future__ import FeatureName¿

            to use the feature in question,
            (but may continue to use such imports)



    Instances of class _Feature have two corresponding methods:
        .getOptionalRelease()
        .getMandatoryRelease().


    CompilerFlag
        is the  (bitfield)  flag
        that should be passed in the fourth argument
        to the builtin function compile()
            to enable the feature
            in ¿dynamically compiled code¿.

        This flag is stored in the .compiler_flag  attribute
            on _Future instances.
        These values must match the appropriate #defines of CO_xxx flags in Include/cpython/compile.h.


¿No feature line is ever to be deleted from this file.¿
"""

all_feature_names = [
    "nested_scopes"    ,
    "generators"       ,
    "division"         ,
    "absolute_import"  ,
    "with_statement"   ,
    "print_function"   ,
    "unicode_literals" ,
    "barry_as_FLUFL"   ,
    "generator_stop"   ,
    "annotations"      ,
]

__all__ = ["all_feature_names"] + all_feature_names

if 'wf':
    # The CO_xxx symbols are defined here
    # under the same names defined in  ¿code¿.h
    # and used by compile.h,
        # so that an editor search will find them here.
    # However, they're not exported in __all__,
    # because they don't really belong to  this module.

    co_nested                  = 0x0010    # nested_scopes
    co_generator_allowed       = 0         # generators (obsolete, was 0x1000)
    co_future_division         = 0x20000
    co_future_absolute_import  = 0x40000   #  absolute imports by default
    co_future_with_statement   = 0x80000
    co_future_print_function   = 0x100000
    co_future_unicode_literals = 0x200000
    co_future_barry_as_bdfl    = 0x400000
    co_future_generator_stop   = 0x800000  # stopiteration becomes runtimeerror in generators
    co_future_annotations      = 0x1000000 # annotations become strings at runtime


class _Feature:

    def __init__(self, optionalRelease, mandatoryRelease, compiler_flag):
        self.optional      = optionalRelease
        self.mandatory     = mandatoryRelease
        self.compiler_flag = compiler_flag

    def getOptionalRelease(self):
        """Return first release in which this feature was recognized.

        This is a 5-tuple, of the same form as sys.version_info.
        """
        return self.optional

    def getMandatoryRelease(self):
        """Return release in which this feature will become mandatory.

        This is a 5-tuple, of the same form as sys.version_info,
        or,
        if  the feature was dropped, is None.
        """
        return self.mandatory

    def __repr__(self):
        return "_Feature" + repr((self.optional,
                                  self.mandatory,
                                  self.compiler_flag))

if 'instances' :
    nested_scopes = _Feature((2, 1, 0, "beta",  1),
                            (2, 2, 0, "alpha", 0),
                            CO_NESTED,
                            )

    generators = _Feature((2, 2, 0, "alpha", 1),
                        (2, 3, 0, "final", 0),
                        CO_GENERATOR_ALLOWED,
                        )

    division = _Feature((2, 2, 0, "alpha", 2),
                        (3, 0, 0, "alpha", 0),
                        CO_FUTURE_DIVISION,
                    )

    absolute_import = _Feature((2, 5, 0, "alpha", 1),
                            (3, 0, 0, "alpha", 0),
                            CO_FUTURE_ABSOLUTE_IMPORT)

    with_statement = _Feature((2, 5, 0, "alpha", 1),
                            (2, 6, 0, "alpha", 0),
                            CO_FUTURE_WITH_STATEMENT)

    print_function = _Feature((2, 6, 0, "alpha", 2),
                            (3, 0, 0, "alpha", 0),
                            CO_FUTURE_PRINT_FUNCTION)

    unicode_literals = _Feature((2, 6, 0, "alpha", 2),
                                (3, 0, 0, "alpha", 0),
                                CO_FUTURE_UNICODE_LITERALS)

    barry_as_FLUFL = _Feature((3, 1, 0, "alpha", 2),
                            (4, 0, 0, "alpha", 0),
                            CO_FUTURE_BARRY_AS_BDFL)

    generator_stop = _Feature((3, 5, 0, "beta", 1),
                              (3, 7, 0, "alpha", 0),
                              CO_FUTURE_GENERATOR_STOP,
                             )

    annotations = _Feature((3, 7, 0, "beta", 1),
                           (3, 11, 0, "alpha", 0),
                           CO_FUTURE_ANNOTATIONS,
                          )

